Asymmetric dual directional steerable catheter sheath

ABSTRACT

A steerable catheter sheath for use in directing a catheter into a desired position is provided. The sheath includes an elongated member configured to receive the catheter therein. The distal end of the elongated member is steerable in two directions, each direction having a different bent configuration, e.g., a sharp curve in one direction and an open arching curve in the other direction. A resilient structure having different bending properties in each of its lateral sides is carried in the distal portion of the elongated member and causes the asymmetric bending. In one embodiment, the resilient structure includes a hypotube with a plurality of notches and slits in the sides. In another embodiment, the resilient structure is covered in an outer coating having different durometer portions. The sheath is particularly useful for accessing left and right pulmonary veins when a transeptal entry approach is used into the left atrium.

RELATED APPLICATION DATA

The present application claims the benefit under 35 U.S.C. §119 to U.S.provisional patent application Ser. No. 61/154,244, filed Feb. 20, 2009.The foregoing application is hereby incorporated by reference into thepresent application in its entirety.

FIELD OF THE INVENTION

The disclosed inventions generally relate to systems and methods forintroducing a medical probe adjacent to target tissue, and moreparticularly to a steerable sheath for intravascularly introducing andpositioning a catheter into a body cavity, such as a heart chamber.

BACKGROUND OF THE INVENTION

Normal sinus rhythm of the heart begins with the sinoatrial node (or “SAnode”) generating an electrical impulse. The impulse usually propagatesuniformly across the right and left atria and the atrial septum to theatrioventricular node (or “AV node”). This propagation causes the atriato contract in an organized manner to transport blood from the atria tothe ventricles, and to provide timed stimulation of the ventricles. TheAV node regulates the propagation delay to the atrioventricular bundle(or “HIS” bundle). This coordination of the electrical activity of theheart causes atrial systole during ventricular diastole. This, in turn,improves the mechanical function of the heart. Atrial fibrillationoccurs when anatomical obstacles in the heart disrupt the normallyuniform propagation of electrical impulses in the atria. Theseanatomical obstacles (called “conduction blocks”) can cause theelectrical impulse to degenerate into several circular wavelets thatcirculate about the obstacles. These wavelets, called “reentrycircuits,” disrupt the normally uniform activation of the left and rightatria.

Because of a loss of atrioventricular synchrony, people who suffer fromatrial fibrillation and flutter also suffer the consequences of impairedhemodynamics and loss of cardiac efficiency. They are also at greaterrisk of stroke and other thromboembolic complications because of loss ofeffective contraction and atrial stasis.

One surgical method of treating atrial fibrillation by interruptingpathways for reentry circuits is the so-called “maze procedure,” whichrelies on a prescribed pattern of incisions to anatomically create aconvoluted path, or maze, for electrical propagation within the left andright atria. The incisions direct the electrical impulse from the SAnode along a specified route through all regions of both atria, causinguniform contraction required for normal atrial transport function. Theincisions finally direct the impulse to the AV node to activate theventricles, restoring normal atrioventricular synchrony. The incisionsare also carefully placed to interrupt the conduction routes of the mostcommon reentry circuits. The maze procedure has been found veryeffective in curing atrial fibrillation. However, not only is the mazeprocedure technically difficult to do, it also requires open heartsurgery and is very expensive.

Maze-like procedures have also been developed utilizingelectrophysiology procedures, which involve forming lesions on theendocardium (the lesions being 1 to 15 cm in length and of varyingshape) using an ablation catheter to effectively create a maze forelectrical conduction in a predetermined path. The formation of theselesions by soft tissue coagulation (also referred to as “ablation”) canprovide the same therapeutic benefits that the complex incision patternsof the surgical maze procedure presently provides, but without invasiveopen heart surgery.

Frequently, an arrhythmia aberration resides at the base, or within oneor more pulmonary veins, wherein the atrial tissue extends. To treatsuch an aberration, physicians use one or more catheters to gain accessinto interior regions of the pulmonary vein tissue for mapping andablating targeted tissue areas. Placement of mapping and ablationcatheters, or alternatively a combined mapping/ablation catheter, withinthe vasculature of the patient is typically facilitated with the aid ofan introducer guide sheath and/or guide wire.

The introducer guide sheath may be introduced into the left atrium ofthe heart using a conventional retrograde approach, i.e., through therespective aortic and mitral valves of the heart. Alternatively, a moresimple approach is to introduce the introducer guide sheath into theleft atrium using a transeptal approach, i.e., through the atrial septum(i.e., fossi ovalis). A detailed description of methods for introducingan introducer guide sheath into the left atrium via a transeptalapproach is disclosed in U.S. Pat. No. 5,575,810, issued to Swanson etal., which is fully and expressly incorporated herein by reference. Oncethe guide sheath is inside the left atrium, the catheter must beadvanced through the guide sheath, into the left atrium, and thenmaneuvered into or adjacent to a desired pulmonary vein (typically withthe aid of a guidewire) before mapping and/or ablating. The pulmonaryvein may be one of the two left pulmonary veins or one of the two rightpulmonary veins.

Positioning of the sheath and guidewire are critical to the success ofthis procedure, since they are the conduit for the ablation catheterand/or mapping catheter. However, the anatomical location of the atrialseptum is closer in proximity to the right pulmonary veins than it is tothe left pulmonary veins. Thus, once the guide sheath passes through theatrial septum, the right pulmonary veins are substantially immediatelyadjacent to the distal end of the guide sheath while the left pulmonaryveins are located on substantially the opposite side of the left atriumfrom the distal end of the guide sheath. As a result, the guide sheathmust be maneuvered differently when placing the catheter in contact withthe left pulmonary veins as opposed to the right pulmonary veins. Whilesteerable guide sheaths can be used to facilitate the introduction ofthe catheter within the desired pulmonary vein, the simple curvesprovided by such steerable guide sheaths do not easily allow theguidance of the catheter within both the left and right pulmonary veins.

SUMMARY OF THE DISCLOSED INVENTIONS

In accordance with a first aspect of the disclosed inventions, asteerable catheter sheath is provided. The sheath comprises an elongatedmember with a distal end, a proximal end and a lumen extending betweenthe proximal end and the distal end, wherein the lumen is configured forreceiving a catheter therein. In one embodiment, the sheath also has ahandle coupled to the proximal end of the elongated member and asteering mechanism mounted to the handle. In order to steer the sheathin two directions, the sheath includes first and second steering wiresthat extend through the elongated member. The distal end of the firststeering wire is coupled to a first lateral side of the elongatedmember, wherein tensioning the first steering wire bends the distal endof the elongated member in a first direction to create a first bendingconfiguration. The distal end of the second steering wire is coupled toa second lateral side of the elongated member, wherein tensioning thesecond steering wire bends the distal end of the elongated member in asecond direction to create a second bending configuration.

If a handle with a steering mechanism is present, the proximal ends ofthe first and second steering wires are coupled to the steeringmechanism, such that operation of the steering mechanism tensions one ofthe first and second steering wires. A shape of the first bendingconfiguration is different from a shape of the second bendingconfiguration. The first bending configuration has a first radius ofcurvature, and the second bending configuration has a second radius ofcurvature, wherein the first and second radii of curvature differ. Inone embodiment, the first bending configuration is configured forpointing the distal end of the elongated member towards a rightpulmonary vein and the second bending configuration is configured forpointing the distal end of the elongated member towards a left pulmonaryvein when the elongated member is introduced into the left atriumthrough the atrial septum.

In an exemplary embodiment, the elongated member comprises an elongatedresilient structure having first and second lateral sides to which thedistal ends of the first and second steering wires are respectivelyaffixed. The first and second lateral sides of the resilient structureare opposite to each other and have different bending properties. In afurther exemplary embodiment, a fulcrum point of the first lateral sideof the resilient structure is distal to a fulcrum point of the secondlateral side of the resilient structure. In one embodiment, theresilient structure comprises a tube having a first plurality of notchesin a first lateral side of the tube and a second plurality of notches ina second lateral side of the tube. The first plurality of notches areconfigured for bending the distal end of the elongated member into thefirst bending configuration and the second plurality of notches areconfigured for bending the distal end of the elongated member into thesecond bending configuration. The tube further comprises a plurality ofslits in a portion of the first lateral side of the tube for allowingthe portion of the tube to bend when the elongated member is steeredinto the second bending configuration and preventing the portion of thetube from bending when the elongated member is steered into the firstbending configuration. A fulcrum point of the first lateral side of thetube is located between the slits and the notches on the first lateralside of the tube. Additionally, the fulcrum point of the first lateralside of the tube is distal to a fulcrum point of the second lateral sideof the tube.

In another embodiment, the resilient structure comprises a coil and anouter coating, the outer coating having a first portion disposed over afirst lateral side of the coil, and a second portion disposed over asecond lateral side of the coil, wherein the first and second portionshave different durometers. In an exemplary embodiment, the first portionof the coating is disposed over a distal region of the first lateralside of the coil, the second portion of the coating is disposed over thesecond lateral side of the coil, and a third portion of the coating isdisposed over a proximal region of the first lateral side of the coil.

In a further exemplary embodiment, the first, second, and third portionsall have different durometers. For example, the first portion has a lowdurometer, the second portion has a medium durometer, and the thirdportion has a high durometer.

In another embodiment, a fulcrum point of the first lateral side of thecoil is between the distal region and the proximal region of the firstlateral side of the coil. Additionally, the fulcrum point of the firstlateral side of the coil is distal to a fulcrum point of the secondlateral side of the coil.

In one embodiment, a catheter assembly is provided that includes thesteerable catheter sheath as described above and a catheter disposedwithin the lumen of the elongated member. In an exemplary embodiment,the catheter is a tissue ablation catheter.

In accordance with yet another aspect of the disclosed inventions, amethod of using the catheter assembly described above is provided. Themethod includes introducing the elongated member into a left atrium. Inone embodiment, the elongated member is introduced into the left atriumusing a transeptal approach where the elongated member passes from aright atrium through an atrial septum into the left atrium. The methodfurther comprises tensioning the first steering wire to bend theelongated member in the first direction into the first bendingconfiguration to point the distal end of the elongated member towards aright pulmonary vein. Once the distal end is in a desired position, theablation catheter is advanced through the lumen of the elongated membersuch that the ablation catheter distally extends from the elongatedmember to contact a first target tissue site within or adjacent to theright pulmonary vein. The ablation catheter is then operated to ablatethe first target tissue site. After ablation of the first target tissuesite, the catheter is retracted into the elongated member.

In an exemplary embodiment, the method further comprises tensioning thesecond steering wire to bend the elongated member in the seconddirection into the second bending configuration to point the distal endof the elongated member towards a left pulmonary vein. Once the distalend is in a desired position, the ablation catheter is again advancedthrough the lumen of the elongated member such that the ablationcatheter distally extends from the elongated member to contact a secondtarget tissue site within or adjacent to the left pulmonary vein. Thecatheter is then operated to ablate the second target tissue site. Afterthe second target tissue site is ablated, the ablation catheter is againretracted into the elongated member.

In one embodiment, the steps of tensioning the first steering wire andtensioning the second steering wire may be performed by operating asteering mechanism on the proximal end of the elongated member. In afurther embodiment, tensioning the first steering wire causescompression of a first lateral side of a resilient structure carried bythe distal end of the elongated member and tensioning the secondsteering wire causes compression of a second lateral side of theresilient structure. Still further, in one embodiment, tensioning thefirst steering wire comprises compressing the first lateral side of theresilient structure and expanding the second lateral side of theresilient structure and tensioning the second steering wire comprisescompressing the second lateral side of the resilient structure andexpanding the first lateral side of the resilient structure.

In accordance with still another aspect of the disclosed inventions, amethod for positioning a catheter is provided. The method includesintroducing a catheter guide sheath into an anatomical cavity;introducing the catheter into the guide sheath; deflecting a distal endof the guide sheath in a first direction into a first bendingconfiguration to point the distal end of the guide sheath towards afirst target site; operating the catheter to perform a medical procedureat the first target site; deflecting the distal end of the guide sheathin a second direction into a second bending configuration different fromthe first bending configuration to point the distal end of the guidesheath toward a second target site different from the first target site;and operating the catheter to perform another medical procedure at thesecond target site.

In an exemplary embodiment, the method also includes advancing thecatheter within the guide sheath until a distal end of the catheterextends distally from the distal end of the guide sheath adjacent to thefirst target site when the distal end of the guide sheath is in thefirst bending configuration; retracting the catheter within the guidesheath prior to deflecting the distal end of the guide sheath into thesecond bending configuration; and advancing the catheter within theguide sheath until the distal end of the catheter extends distally fromthe distal end of the guide sheath adjacent to the second target sitewhen the distal end of the guide sheath is in the second bendingconfiguration.

In one embodiment, the anatomical cavity is a heart chamber, the firsttarget site is a right pulmonary vein, and the second target site is aleft pulmonary vein. In a further embodiment, the method includespassing the distal end of the guide sheath from a right atrium to a leftatrium through a septal wall. In an exemplary embodiment, the medicalprocedures are ablation procedures.

In a further exemplary embodiment, the method comprises operating asteering mechanism coupled to a proximal end of the guide sheath todeflect the distal end of the guide sheath into the first bendingconfiguration and the second bending configuration. In a still furtherexemplary embodiment, deflecting the distal end of the guide sheath inthe first direction comprises tensioning a first steering wire, anddeflecting the distal end of the guide sheath in the second directioncomprises tensioning a second steering wire.

Although the disclosed inventions should not be so limited in theirbroadest aspects, the use of a steerable catheter sheath in the mannerdescribed above allows a user to position the catheter sheath near atarget ablation site before the catheter is deployed from the sheath,thereby decreasing the distance traveled by the catheter between thedistal end of the sheath and the target tissue site and increasing theease with which the catheter is retracted back into the sheath after theablation procedure.

Other features of the disclosed inventions will become apparent fromconsideration of the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the disclosed inventions, in which similar elements are referred toby common reference numerals, and in which:

FIG. 1A is a plan view of a catheter assembly including an ablationcatheter and a steerable catheter sheath constructed in accordance withthe disclosed inventions;

FIG. 1B is a plan view of the steerable catheter sheath constructed inaccordance with the disclosed inventions with a first bent configurationand a second bent configuration shown in phantom;

FIG. 2A is a cross-sectional view of the steerable catheter sheath takenalong line 2A-2A in FIG. 1A;

FIG. 2B is a cross-sectional view of the steerable catheter sheath takenalong line 2B-2B in FIG. 2A;

FIG. 3A is a plan view of a first embodiment of a resilient structure;

FIGS. 3B and 3C are plan views of the first embodiment of the resilientstructure in the first bent configuration and the second bentconfiguration, respectively;

FIG. 4A is a plan view of a second embodiment of a resilient structureand an outer coating shown in phantom;

FIGS. 4B and 4C are cross-sectional views of the steerable cathetersheath, according to the second embodiment, taken along lines 4B-4B and4C-4C, respectively, of FIG. 4A;

FIGS. 4D and 4E are cross-sectional views of the steerable cathetersheath, taken along line 4D-4D of FIG. 4C, in the first bentconfiguration and the second bent configuration, respectively;

FIG. 4F is a plan view of the distal portion of the steerable cathetersheath with the outer coating constructed in accordance with the secondembodiment; and

FIGS. 5A-5E are plan views of steps in a method of using the catheterassembly shown in FIG. 1A to direct a catheter into a desired position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1A, 1A, 2A, and 2B, an exemplary assembly 200constructed in accordance with the disclosed inventions is shown. Theassembly 200 includes a catheter 100 and a steerable catheter sheath 10sized for receiving the catheter 100 therein. In the illustratedembodiment, the catheter 100 is an ablation catheter or amapping/ablation catheter and carries ablation and/or mapping elementson a distal end 102 thereof. The assembly 200 may further include aguide wire and/or other therapeutic tools (not shown) to be deliveredinto the left atrium in a desired position.

Although the steerable catheter sheath 10 is described hereinafter foruse in the heart for facilitating introduction of the catheter 100 intodesirable positions for mapping and ablating arrhythmia substrates, thesheath 10 may be used within any body lumens, chambers or cavities of apatient for therapeutic and diagnostic purposes in those instances whereaccess to interior bodily regions is obtained through, for example, thevascular system or alimentary canal and without complex invasivesurgical procedures. For example, the sheath 10 also has application inthe treatment of ailments of the gastrointestinal tract, prostrate,brain, gall bladder, uterus, and other regions of the body.

The sheath 10 generally comprises an elongated body 12, a handle 14coupled to a proximal end 15 of the elongated body 12, and a lumen 30extending through the elongated body 12 for allowing the catheter 100,guide wire (not shown), and/or other therapeutic tools (also not shown)to be inserted from a proximal end of the handle 14 towards a distal end13 of the elongated body 12, as indicated by arrow 16 in FIG. 1A. Theelongated body 12 includes a proximal portion 21 and a steerable distalportion 23.

The distal end 13 of the elongated body 12 is configured to beintroduced through the vasculature of the patient, and into ananatomical cavity, such as the left atrium of the heart. The distalportion 23 is configured to selectively bend in two directions, eachbending direction having its own specific configuration, as shown inphantom in FIG. 1B. The curvature assumed by bending the distal portion23 to the right is different from the curvature assumed by bending thedistal portion 23 to the left. For instance, when deflected to theright, the distal portion 23 assumes a first configuration 18, e.g. asubstantially open arch curved profile with a first predeterminedcircumference. In contrast, when deflected to the left, the distalportion 23 assumes a second configuration 20, e.g. a sharply curvedprofile with a second predetermined circumference. These different leftand right curvatures are referred to herein as asymmetric curves.

In an exemplary embodiment, the second configuration 20 has asubstantially smaller radius of curvature than that of the firstconfiguration 18. The specific circumferences, radii of curvature, andshapes that the distal portion 23 will assume is related to parameterssuch as the size, shape, material of construction, and location ofvarious elements of the elongated body 12. It should be well understoodthat any desired circumference, radius of curvature, and shape of thetwo bent configurations may be achieved by adjusting such parameters.

The proximal portion 21 of the elongated body 12 is formed of acomposite of Pebax® and stainless steel, or other suitable materials, inthe form of a braid, coil, or combination thereof, so that the proximalportion 21 of the elongated body 12 has desired stiffness and torsionalproperties. The distal portion 23 of the elongated body 12 is formed ofa more flexible material so that the distal portion 23 has desiredbending properties. The distal portion 23 comprises an elongatedresilient structure 24 shown in phantom in FIG. 1A. As best shown inFIGS. 2A and 2B, the distal portion 23 of the elongated body 12 includesa lubricious inner coating 26 disposed on the inner surface of theresilient structure 24 to reduce friction during movement of a catheteror guide wire through the lumen 30, and an outer coating 22 disposed onthe outer surface of the resilient structure 24. The resilient structure24 may be composed of a suitable resilient material, such as stainlesssteel or nitinol. The inner coating 26 may be PTFE or the like, and theouter coating 22 may be Pebax®, polyethylene, polyurethane, polyolefin,or any other suitable polymeric or bio-compatible material.

The sheath 10 further comprises a steering mechanism 17 incorporatedinto the handle 14, and a pair of right and left steering wires 28 a, 28b extending through the elongated body 12. The steering mechanism 17 isoperable to selectively tension the steering wires 28 a, 28 b, therebytransforming the distal portion 23 of the elongated body 12 from itsstraight geometry, shown in FIG. 1A, into one of its curved geometries,shown in FIG. 1B.

To this end, the proximal ends of the steering wires 28 a, 28 b arecoupled to the steering mechanism 17 in the handle 14, while the distalends of the steering wires 28 a, 28 b are welded or otherwise affixed toa steering ring 27 that is disposed between the inner coating 26 and theresilient structure 24, as shown in FIGS. 2A and 2B. In particular, oneof the steering wires (in this case, the right steering wire 28 a) isattached to the right lateral side of the steering ring 27 and the othersteering wire (in this case, the left steering wire 28 b) is attached tothe left lateral side of the steering ring 27. The steering wires 28 aand 28 b may alternatively or additionally be affixed to oppositelateral sides of the resilient structure 24. The steering wires 28 a and28 b are free to slide within the space 25 between the resilientstructure 24 and the inner liner 26. In an exemplary embodiment, thesteering wires 28 a and 28 b are coated (i.e. with Teflon®, not shown)to reduce friction caused by the steering wires 28 a and 28 b movingrelative to the resilient structure 24 and the inner coating 26. Furtherdetails of exemplary steering mechanisms can be found in U.S. Pat. Nos.6,579,278, 6,198,974, 5,358,478 and 5,273,535, which are expresslyincorporated herein by reference.

It should be well understood that, although FIGS. 2A and 2B depict theresilient structure 24 extending over the steering ring 27, theresilient structure 24 may alternatively not extend over the steeringring 27. It should also be well understood that, although the steeringwires 28 a, 28 b and steering ring 27 are depicted as being attached tothe distal end 13 of the elongated body 12, the attachment mayalternatively be proximal to the distal end 13, depending on the desiredbending configurations. In a further alternative, the steering wires 28a and 28 b may be attached at different lateral positions along theelongated body 12, in which case the elongated body 12 may include twosteering rings wherein the steering wires 28 a and 28 b are eachattached to a different steering ring.

The asymmetric bending of the distal portion 23 of the elongated body 12results from different bending properties and different fulcrum pointpositions on the respective lateral sides 12 a and 12 b of the distalportion 23 of the elongated body 12. There are various ways to achievethe different bending properties and fulcrum point positions. Forexample, the different bending properties and fulcrum point positionsmay be incorporated in the resilient structure 24 and/or the outercoating 22 where opposite lateral sides of the resilient structure 24and/or the outer coating 22 are configured to bend differently when thesteering mechanism 17 is operated.

Referring to FIGS. 3A-3C, in an exemplary embodiment, the resilientstructure 24 comprises an elongated hypotube 32, a plurality of lasercuts or notches 34 on the right lateral side 32 a of the tube 32, and aplurality of laser cuts or notches 33 and a plurality of slits 36 on aleft lateral side 32 b of the tube 32. The notches 33, 34, and slits 36are configured in a manner that facilitates the bi-directionalasymmetric deflection of the distal portion 23 of the elongated body 12.Specifically, the notches 34 are located between a right side fulcrumpoint 37 and the distal end 13, the notches 33 are located between aleft side fulcrum point 35 and the distal end 13, and the slits 36 arelocated proximal to the left side fulcrum point 35, but distal to theright side fulcrum point 37. It should be understood that the slits 36and notches 33 and 34 can be configured to achieve substantially anydesired curve circumference, shape, and fulcrum point position, as longas the bi-directional asymmetric deflection of the distal end 13 can beachieved. Thus, the slits 36 and notches 33 and 34 may alternativelyhave sizes and shapes that are different from those depicted in FIGS.3A-3C.

The size, shape and spacing of the notches 34 on the right lateral side32 a of the hypotube 32 are configured so that, when the right steeringwire 28 a (not shown here for clarity; see FIGS. 2A-2B) is tensioned,the distal portion 23 of the elongated body 12 will bend into the firstconfiguration 18 by compressing the notches 34 on the right lateral side32 a, while expanding the notches 33 and slits 36 on the left lateralside 32 b, as shown in FIG. 3B. The size, shape and spacing of thenotches 33 and the slits 36 on the left lateral side 32 b of thehypotube 32 are configured so that, when the left steering wire 28 b(not shown here for clarity; see FIGS. 2A-2B) is tensioned, the distalend 13 of the elongated body 12 will bend into the second configuration20 by compressing the notches 33 on the left lateral side 32 b whileexpanding the notches 34 on the right lateral side 32 a, as shown inFIG. 3C. Substantially the entire hypotube 32 is free to bend whensteered into the first configuration 18. However, the slits 36 arealready completely compressed and do not collapse upon one another,thereby preventing a proximal portion 38 of the hypotube 32 from bendingwhen the hypotube 32 is directed into the second configuration 20.

Referring to FIGS. 4A-4F, in another exemplary embodiment, the resilientstructure 24 comprises an elongated coil 42 and the outer coating 22includes portions 22 a, 22 b and 22 c with different durometers. Theleft lateral side distal portion 22 a of the coating has a lowdurometer, the right lateral side portion 22 b of the coating has amedium durometer, and the left lateral side proximal portion 22 c has ahigh durometer. Thus, the stiffness of the outer coating 22 is notuniform, but varies along its length and circumference. The stiffestpart of the coating 22 is the left lateral side proximal portion 22 c,which is substantially equal in durometer to the coating 22 covering therest of the elongated body 12 proximal to the resilient structure 24, asbest depicted in FIG. 4F.

Each portion 22 a, 22 b and 22 c of the coating extends about halfwayaround the circumference of the coil 42, as depicted in FIGS. 4B, 4C and4F. However, it should be well understood that the portions 22 a, 22 band 22 c may extend around less than half of the circumference of thecoil 42 or more than half the circumference of the coil 42. The portions22 a, 22 b and 22 c of the coating 22 may be formed by co-extrusion,compression melting, flow melting and/or the like. In one embodiment,the coating 22 is applied to the coil 42 by positioning the coil 42within the coating 22 (which will take the form of a tube) and heatshrinking or the like.

The coating 22 is arranged, such that a fulcrum point 45 is formedbetween the left lateral side distal portion 22 a and the left lateralside proximal portion 22 c of the coating, and a fulcrum point 47 isformed just proximal to the right lateral side portion 22 b of thecoating, with the fulcrum point 45 being distal to the fulcrum point 47.Thus, the durometers and relative locations of the coating portions 22a, 22 b and 22 c are arranged so that when the right steering wire 28 ais tensioned, the distal end 13 of the elongated body 12 will bend intothe first configuration 18 by compressing the right lateral side 42 a ofthe coil while expanding the left lateral side 42 b of the coil, asshown in FIG. 4D, and when the left steering wire 28 b is tensioned, thedistal end 13 of the elongated body 12 will bend into the secondconfiguration 20 by compressing the left lateral side 42 b of the coil,while expanding the right lateral side 42 a of the coil, as shown inFIG. 4E. It should be understood that the coating 22 and the coil 42 canbe configured to achieve substantially any desired curve circumference,shape, and fulcrum point position, as long as the bi-directionalasymmetric deflection of the distal end 13 can be achieved.

In general, the asymmetric curves provide the user with flexibility insteering the catheter guide sheath 10 into position. The asymmetriccurves of the distal portion 23 of the elongated body 12 may beespecially advantageous when a transeptal approach is used for enteringinto the left atrium, i.e., since the first predetermined circumferenceis larger than the second predetermined circumference, the firstconfiguration 18 is used to point the distal end 13 of the elongatedbody 12 towards the left pulmonary veins and the second configuration 20is used to point the distal end 13 of the elongated body 12 towards theright pulmonary veins. Positioning the distal end 13 of the elongatedbody 12 as close to a target location as possible reduces the distancethat an ablation or mapping catheter must distally extend out of thedistal end 13 and retraction of the catheter proximally back into theelongated body 12 is simplified.

Having described the structure of the catheter guide sheath 10, itsoperation in positioning the mapping and/or ablation catheter 100 neartarget tissue in the left and right pulmonary veins within the leftatrium of the heart will now be described with reference to FIGS. 5A-5E.It should be noted that other regions within the heart can also betargeted using the steerable catheter guide sheath 10. First, as shownin FIG. 5A, the guide sheath 10 is introduced into the left atrium 62 ofthe heart 64 using a transeptal approach. A guide catheter or guide wire(not shown) may be used in association with the guide sheath 10 to aidin directing the guide sheath 10 through the appropriate artery towardthe heart 64 (i.e., through the inferior vena cava or superior vena cavainto the right atrium).

Once the distal end 13 of the elongated body 12 passes through theatrial septum 66, the steering mechanism 17 on the handle 14 (not shownhere; see FIGS. 1A and 1B) of the sheath 10 is operated to tension theright steering wire 28 a (shown in FIGS. 2A and 2B) to steer the distalend 13 into the first bending configuration 18 to point the distal end13 towards the left pulmonary veins 67, as shown in FIG. 5B. Once thedistal end 13 is properly placed, the catheter 100 is advanced throughthe lumen 30 in the elongated body 12 until the distal end 102 of thecatheter 100 extends distally from the elongated body 12 and contacts afirst target tissue site in or around the left pulmonary veins 67, asshown in FIG. 5C. Next, the catheter 100 is operated to map and/orablate the first target tissue site.

Once the ablation procedure at the first target tissue site is complete,the catheter 100 is proximally retracted into the elongated body 12.Then, the steering mechanism 17 on the handle 14 of the sheath 10 isoperated to tension the left steering wire 28 b to steer the distal end13 into the second bending configuration 20 to point the distal end 13towards the right pulmonary veins 68, as shown in FIG. 5D. Once thedistal end 13 is properly placed, the catheter 100 is again advancedthrough the lumen 30 of the elongated body 12 until the distal end 102of the catheter 100 extends distally from the elongated body 12 andcontacts a second target tissue site in or around the right pulmonaryveins 68, as shown in FIG. 5E. The catheter 100 is then operated to mapand/or ablate the second target tissue site.

After the mapping/ablation, the catheter 100 is proximally retractedinto the elongated body 12 and the catheter 100 and the sheath 10 areremoved from the patient. It should be well understood that theabove-described ablation procedure could alternatively be performed byfirst steering the catheter sheath 10 towards the right pulmonary veins68 and then steering the catheter sheath 10 towards the left pulmonaryveins 67. Although the method describes only two mapping and/or ablatingprocedures, it should be well understood that the method may includemore than two mapping and/or ablating procedures. For example, themethod may includes multiple mapping and/or ablating procedures whilethe sheath 10 is in the first bending configuration 18 before steeringthe sheath 10 into the second bending configuration 20.

Although particular embodiments of the disclosed inventions have beenshown and described, it will be understood that it is not intended tolimit the disclosed inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the scope of theinventions.

For example, although the bending directions of the catheter guidesheath are shown as being 180 degrees apart, it should be understoodthat the bending directions may be greater than or less than 180 degreesapart. By way of another example, the bending directions may be 90degrees apart. Further, although the catheter guide sheath is shown ashaving two bent configurations, it should be understood that the sheathmay have more than two bent configurations. By way of yet anotherexample, the catheter guide sheath may have three or four bentconfigurations that may be symmetrically or asymmetrically disposedaround a central axis. Still further, rather than the outer coating 22with different durometer sections depicted in FIGS. 4A-4F, the coil 42may be formed of a coated wire where the wire coating has sections withvarying stiffness profiles. In other words, the coil 42 may includesections with varying bending properties, while the outer coating hasuniform bending properties.

Thus, the disclosed inventions are intended to cover alternatives,modifications, and equivalents, which may be included within the scopeof the disclosed inventions, as limited and defined only by thefollowing claims and their equivalents.

What is claimed is:
 1. A steerable catheter sheath, comprising: anelongated member having a distal end, a proximal end and a lumenextending between the proximal end and the distal end, wherein the lumenis configured for receiving a catheter therein, the elongated membercomprising an elongated resilient tube having a first plurality ofnotches in a first lateral side thereof and a second plurality ofnotches in a second lateral side thereof, and wherein the respectivefirst and second lateral sides of the tube have different bendingproperties; a first steering wire comprising a distal end coupled to thefirst lateral side of the elongated member, wherein tensioning the firststeering wire bends the distal end of the elongated member in a firstdirection to create a first bending configuration; and a second steeringwire comprising a distal end coupled to the second lateral side of theelongated member, wherein tensioning the second steering wire bends thedistal end of the elongated member in a second direction to create asecond bending configuration, wherein a shape of the first bendingconfiguration is different from a shape of the second bendingconfiguration; wherein the tube further comprises a plurality of slitsin a portion of the first lateral side of the tube for allowing theportion of the tube to bend when the elongated member is steered intothe second bending configuration and preventing the portion of the tubefrom bending when the elongated member is steered into the first bendingconfiguration, and wherein a fulcrum point of the first lateral side ofthe tube is located between the slits and the notches in the firstlateral side of the tube distal to a fulcrum point of the second lateralside of the tube.
 2. The steerable catheter sheath of claim 1, furthercomprising a handle coupled to the proximal end of the elongated member;and a steering mechanism mounted to the handle, wherein the first andsecond steering wires have proximal ends coupled to the steeringmechanism, such that operation of the steering mechanism tensions one ofthe first and second steering wires.
 3. The steerable catheter sheath ofclaim 1, wherein the first bending configuration has a first radius ofcurvature, and the second bending configuration has a second radius ofcurvature different from the first radius of curvature.
 4. The steerablecatheter sheath of claim 1, wherein the first plurality of notches areconfigured for bending the distal end of the elongated member into thefirst bending configuration and the second plurality of notches areconfigured for bending the distal end of the elongated member into thesecond bending configuration.
 5. A catheter assembly, comprising: thesteerable catheter sheath of claim 1; and the catheter of claim 1,wherein the catheter is a tissue ablation catheter disposed within thelumen of the elongated member.
 6. A method of using the catheterassembly of claim 5, comprising: introducing the elongated member from aright atrium through an atrial septum into a left atrium; tensioning thefirst steering wire to bend the elongated member in the first directioninto the first bending configuration to point the distal end of theelongated member towards a right pulmonary vein; advancing the ablationcatheter through the lumen of the elongated member such that theablation catheter distally extends from the elongated member to contacta first target tissue site within or adjacent to the right pulmonaryvein; ablating the first target tissue site with the ablation catheter;retracting the ablation catheter into the elongated member; tensioningthe second steering wire to bend the elongated member in the seconddirection into the second bending configuration to point the distal endof the elongated member towards a left pulmonary vein; advancing theablation catheter through the lumen of the elongated member such thatthe ablation catheter distally extends from the elongated member tocontact a second target tissue site within or adjacent to the leftpulmonary vein; ablating the second target tissue site with the ablationcatheter; and retracting the ablation catheter into the elongatedmember.
 7. The method of claim 6, wherein tensioning the first steeringwire and tensioning the second steering wire comprise operating asteering mechanism on the proximal end of the elongated member.
 8. Themethod of claim 6, wherein tensioning the first steering wire comprisescompressing the first lateral side of the distal end of the elongatedmember; and wherein tensioning the second steering wire comprisescompressing the second lateral side of the resilient tube.
 9. The methodof claim 8, wherein tensioning the first steering wire further comprisescompressing the first lateral side of the resilient tube and expandingthe second lateral side of the resilient tube; and wherein tensioningthe second steering wire further comprises compressing the secondlateral side of the resilient tube and expanding the first lateral sideof the resilient tube.
 10. A method for positioning a catheter in abody, comprising: providing a steerable guide sheath comprising anelongated member having a distal end, a proximal end and a lumenextending between the proximal end and the distal end, wherein the lumenis configured for receiving the catheter therein, the elongated membercomprising an elongated resilient tube having a first plurality ofnotches in a first lateral side thereof and a second plurality ofnotches in a second lateral side thereof, and wherein the respectivefirst and second lateral sides of the tube have different bendingproperties; a first steering wire comprising a distal end coupled to thefirst lateral side of the elongated member, wherein tensioning the firststeering wire bends the distal end of the elongated member in a firstdirection to create a first bending configuration; and a second steeringwire comprising a distal end coupled to the second lateral side of theelongated member, wherein tensioning the second steering wire bends thedistal end of the elongated member in a second direction to create asecond bending configuration, wherein a shape of the first bendingconfiguration is different from a shape of the second bendingconfiguration; wherein the tube further comprises a plurality of slitsin a portion of the first lateral side of the tube for allowing theportion of the tube to bend when the elongated member is steered intothe second bending configuration and preventing the portion of the tubefrom bending when the elongated member is steered into the first bendingconfiguration, and wherein a fulcrum point of the first lateral side ofthe tube is located between the slits and the notches in the firstlateral side of the tube distal to a fulcrum point of the second lateralside of the tube; introducing the steerable guide sheath into ananatomical cavity; introducing the catheter into the guide sheath;deflecting a distal end of the guide sheath in the first direction intothe first bending configuration to point the distal end of the guidesheath towards a first target site; operating the catheter to perform amedical procedure at the first target site; deflecting the distal end ofthe guide sheath in the second direction into the second bendingconfiguration different from the first bending configuration to pointthe distal end of the guide sheath toward a second target site differentfrom the first target site; and operating the catheter to performanother medical procedure at the second target site.
 11. The method ofclaim 10, further comprising: advancing the catheter within the guidesheath until a distal end of the catheter extends distally from thedistal end of the guide sheath adjacent to the first target site whenthe distal end of the guide sheath is in the first bendingconfiguration; retracting the catheter within the guide sheath prior todeflecting the distal end of the guide sheath into the second bendingconfiguration; and advancing the catheter within the guide sheath untilthe distal end of the catheter extends distally from the distal end ofthe guide sheath adjacent to the second target site when the distal endof the guide sheath is in the second bending configuration.
 12. Themethod of claim 10, wherein the anatomical cavity is a heart chamber,the first target site is a right pulmonary vein, and the second targetsite is a left pulmonary vein.